Zinc-containing zeolite catalyst

ABSTRACT

A crystalline-alumino-silicate zeolite catalyst support having high crystalline stability and acidic catalytic activity is prepared from an alkali zeolite, preferably a Y-faujasite, by (1) removing the alkali metal ions to below about 1.0%w by ion exchange, and (2) incorporating zinc ions and calcining at a high temperature of about 800*C. The support can then be combined with hydrogenative metals such as Group VIII and Group VIB, followed by drying and calcining to provide superior hydroisomerization and hydrocracking catalysts.

United States Patent 1 1 Berry 1 Jan. 30, 1973 [54] ZINC-CONTAINING3,449,070 6/l969 McDaniel et al. ..208/l ll CATALYST 3,507,802 4/1970Smith et al, ..252/455 [75] Inventor: Thomas E. Berry, East Alton, Ill.primary Examiner ])e|ben Gantz 73 A Sh 1 C N Y k Assistant Examiner-G.E. Schmitkons 1 S-Slgnee e 0' ompany ew or Att0rneyGlen R. Grunewald etal. [22] Filed: Sept. 15,1971 v 21 App]. No.: 180,828 [571 ABSTRACT 1 Acrystalline-alumino-silicate zeolite catalyst support l Apphcanon Datahaving high crystalline stability and acidic catalytic ac- [60] Divisionof sen NO 1 354 Ja 9 1970 P tivity is prepared from an alkali zeolite,preferably a 3,654,185, which is a continuation-in-part of Ser. No.Y-faujasite, y removing the alkali mctal ions t0 803,091,Feb.27, 1969.below about 1.0%w by ion exchange, and (2) incorporating zinc ions andcalcining at a high temperature [52] US. Cl ..208/111, 208/D1G.2,260/683.65, of about 800C. The support can then be combined 208/138 withhydrogenative metals such as Group VIII and {511' Int. Cl. ..C0'7C 5/22,ClOg 13/02, BOlj 11/40 Group VlB, followed by drying and calcining topro- [58] Field of Search ..208/138', 111; 260/683.65 vide superiorhydroisomerization and hydrocracking I catalysts. [56] 7 ReferencesCited UNITED STATES PATENTS 7 Claims, No Drawings Gladrow et al. ..23/1I l ZINC-CONTAINING ZEOLITE CATALYST CROSS REFERENCE TO RELATEDAPPLICATIONS This application is a divisionof application Ser. No. 1,854filed Jan. 9, 1970 (now U.S. Pat. No. 3,654,l 85), which is acontinuation-in-part of application Ser. No. 803,091,filed Feb. 27,1969. I

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to a new highly active and stable zinc-containing crystallinealumino-silicate zeolite catalyst.

2. Description of the Prior Art Crystalline alumino-silicate zeoliteshave in recent years become of major importance as catalysts andcatalytic components for hydrocarbon conversion reactions. Bothnaturally occuring and synthetically prepared zeolites have demonstratedextraordinary catalytic properties.

Synthetic zeolites are favored since the crystal structure andcompositional purity can be carefully controlled to achieve desiredproperties.

Synthetic zeolites are almost universally prepared in the alkali metal(sodium or potassium) form by crystallizing zeolite from an aqueousreaction mixture containing alumina ,(as sodium aluminate, alumina sol,etc.), silica (as sodium silicate, silica gel or silica sol), and alkalimetal oxides such as sodium hydroxide. The presence of alkali metaloxide initially helps to stabilize the zeolite structure but, as is wellknown, the alkali metal must be replaced, at least partially, to achieveappreciable catalytic activity.

Synthetic faujasites as prepared typically contain in the range of about-1 3%w alkali metal ions. Exchange of the alkali metal for hydrogen ionshas long been recognized as a means of markedly improving catalyticactivity. However, when alkali metal is reduced. to levels below about2%w, the crystal structure becomes unstable and is easily collapsed uponheating, resulting in a substantially amorphous silica-alumina of muchreduced catalytic activity. This phenomenon has been ascribed to adifference in the chemical nature of the bound alkali metal ions in thecrystal structure. It has been proposed that the bulk of the alkali ionsoccupy positions in the structure which do not-fundamentally affect thestructural stability, i.e., in caged positions while the remainingsodium (ca l%w) occupies bridge positions in the crystal and whenremoved result in structural collapse (see Broussard et al, U.S. Pat.No. 3,287,255). al,

It has recently been suggested that very highly stable zeolites can beproduced by a sequence of ion exchange steps to replace alkali metalions in the zeolite interposed with a step of heating the zeolite to atemperature within the range of about l300F (704C) to l600F (871C). Theintermediate heating or calcination step permits alkali metal removal topreviously unobtainable. levels (see Maher et al, U.S. Pat. No.3,293,192). Zeolites having very low alkali metal contents are unstableeven to the intermediate calcination step so that other specialprocedures, such as steeping the highly exchanged zeolite in theexchange solution, are required (Maher et al, U.S. Pat. No. 3,374,056).

SUMMARY OF THE INVENTION In broad aspect the present invention is acrystalline alumino-silicate zeolite having low alkali metal content, astable crystal structure and highly active catalytic activity resultingfrom the inclusion of zinc and calcination at a temperature of about800C. The

zeolite is prepared from an alkali form of crystalline zeolite having afaujasite crystal structure by (1) substantially removing alkali metalions by ion exchange, (2) incorporating zinc ions from an aqueoussolution and (3) calcination at about 800C. The catalysts of thisinvention are used for the hydroisomerization of C -C normal paraffinsas well as for conventional hydrocracking. Preferably, these catalystsare used for single-stage hydrocracking of nitrogen containingfeedstocks or multi'stage hydrocracking where the gaseous conversionproducts are not removed from the first stage before passing theeffluent to a subsequent stage. Zinc contents of the catalysts prior tocalcination range between about 0.5 to 15%w. Preferably, catalysts usedfor hydroisomerization of normal paraffms will have a zinc content fromabout l-6%w prior to calcination, while catalyst used for hydrocrackingfeedstocks having greater than 50 ppm organic nitrogen will have a zinccontent from about 6! 5%w.

DETAILED DESCRIPTION Synthetic crystalline zeolites having structuressimilar to that of the mineral faujasite are the starting materials forthe composition of the present invention. The preferred Y-faujasite hasa composition (based on unit cell formula)'of Na -,,(A10 -,(Si0 x H 0.Y- faujasite has relatively higher silica content and more inherentstructural stability than other zeolites of the faujasite type.Preparation of Y-zeolite and its properties are disclosed in U.S. Pat.No. 3,3 l0,007.

According to the present invention, alkali metal ions in the zeolitestructure are first removed by ion exchange. Ion exchange may be carriedout with any ionic solution but it is preferred that metal ion exchangenot be used since the replacement of alkali metal ion by other metalions (except zinc) have undesirable aspects. For example, silver nitratesolution is very efficient for removal of alkali metal ion butintroduces silver ions which interfere with the desired structuralchanges accomplished by the invention. Ammonium salt solutions, such asfor example, ammonium nitrate, carbonate, sulfate, halides, etc., aresuitable for ion exchange. In most cases, multiple exchanges aredesirable. The exchange is carried out by any conventional exchangeprocedure, either batchwise or continuous and preferably at elevatedtemperatures in the range of C, as for example, by refluxing the zeolitein an exchange solution. Batchwise exchange may be carried out byslurrying the zeolite with an appropriate ammonium compound such as 2 Mammonium nitrate, separating the solution by filtration or settling,then washing with water. This procedure is repeated several times.

Following removal of the alkali metal ions the zeolite is exchanged withan ionic solution of a zinc salt to incorporate zinc ions into thecrystal structure. It should be noted the exchange with zinc tends tofurther reduce the alkali metal content of the zeolite in cases wheresubstantially complete removal has not been achieved in the firstexchange. However, the first exchange is required before exchange withzinc ions.

Any common salt of zinc which will form an ionic aqueous solution may beused for the incorporation of zinc. For example, zinc nitrate, zincacetate and the like are suitable. These salts are especially suitablesince the ions decompose upon calcination and thus do not interfere withthe catalytic activity of the finished composition. The zinc solutionshould be chosen to give a reasonably high concentration of zinc ions(ca 1.0 M or higher) without the necessity for highly acidic conditions.The solution should be maintained above about 3-4 pI-I. Solutions havinga pH as low as 2 tend to dissolve alumina and cause collapse of thecrystalline structure.

While it is recognized that the prior art has suggested the replacementof alkali metal ions in zeolites with various polyvalent ions includingzinc, the present composition is unlike the prior art compositions inseveral respects. The zinc ions are not directly exchanged for alkaliions but are introduced after prior removal or reduction of the alkaliions. In addition, it has been found that zinc ions in combination witha high temperature calcination produces changes in the crystal structurewhich give it exceptional stability and catalytic activity. Thecalcination is critical to the invention and will be subsequentlydescribed. Moreover, zinc exhibits behavior in the final overallpreparation that is experimentally distinguishable from other metalions, such as magnesium, aluminum and beryllium which have been thoughtequivalent to zinc in stabilizing zeolites. In the present inventionexceptional stability is achieved by the coordination of zincincorporation and an intermediate high temperature calcination beforeincorporating hydrogenation metals to produce a compositional entity notknown to the art.

The amount of zinc exchanged into the zeolite prior to the intermediatecalcination should be at least above about 0.5%w and preferably notabove about percent. It is preferred that the amount of zinc be in therange of about l6%w prior to calcination. Additional zinc can beincorporated into the zeolite, if desired, subsequent to the stabilizingintermediate calcination at about 800C.

Following incorporation of zinc to the desired level the zeolite may bewashed to remove any unexchanged ions prior to calcination. Water whichis substantially free of metallic ions has proved a very suitable washmedium. However, washing with non-alkali metal ammonium ion solution isalso suitable. For example, washing with a 2 M solution of ammoniumnitrate at about C gave especially good results. At this temperaturelittle or no further removal of alkali metal ions is accomplished. Whilethis washing step is not essential, it is preferred.

The amount of alkali metal in the zeolite following zinc incorporationwill be below about 1%w. Most favorable results for hydroisomerizationcatalysts are obtained when the final composition contains below about0.5%w alkali metal and particularly about 0.2-0.3%w as will be shown inthe accompanying examples. Alkali metal contents below 0.5%w are alsopreferred for hydrocracking catalysts.

An intermediate calcination of a zeolite having zinc ions selectivelyplaced in the crystal structure is a critical and essential feature ofthe method of the invention. It is this step which gives the zinczeolite its exceptional structural stability. The reason for thestabilization of the structure by intermediate calcination is notclearly understood but is believed to be related to a rearrangement ofthe molecular coordination, at least in part, from a tetrahedral totrigonal bonding of the siliconaluminum-oxygen system. It is believedthat the inclusion of zinc ions plays an important part in thestructural transformation. It has been found, for example, that theinclusion of magnesium, having properties obstensibly the same as zinc,interferes with, rather than coordinates with this transformation. Thus,the cooperation of the zinc ion and the structural change brought aboutby the calcination at about 800C work in combination to produce theproduct of the invention. In any case, the intermediate calcination isrequired before the hydrogenation metals are incorporated and thetemperature must be controlled over a narrow critical range. Calcinationbelow about 775C is not effective to accomplish the desired results andtemperatures above about 825C result in structural damage. Therefore,calcination should be closely controlled to about 800C. Atmosphericpressure is suitable for the calcination treatment, pressure not being avariable of critical importance. The time of calcining after reachingabout 800C is not especially critical, but should be continued forsufficient time to remove water physically associated with the catalystl hour should suffice but longer periods can be used. It is especiallypreferred that calcination be carried out for about 1-5 hours in stillair.

The zinc content of the finished catalyst composition may be variedfollowing calcination. Thus, the amount of zinc may be reduced byexchange for other metal cations or for hydrogen. For some applications,it may be desirable to exchange additional zinc into the zeolite. Forexample, zinc contents on the finished catalyst from about 6-9%w arepreferred for hydrocracking feedstocks having greater than 50 ppmorganic nitrogen.

When hydrogenation metals are incorporated, as discussed below, somezinc is usually removed, reducing the level below that present prior tocalcination. Ion exchange procedures as disclosed for initialincorporation of zinc, above are suitable, for variation in zinc levelafter calcination. Insofar as crystal stability is concerned, the amountof zinc in the final composition is not especially critical, the levelduring the calcination at about 800C being the determinative factor.

For many catalytic applications the novel zeolite material of theinvention is preferably composited with hydrogenative metal componentssuch as metals of Group VIB (Cr, Mo, W) and Group VIII (Ni, Co, Fe, Ptand Pd) of the Periodic Table of Elements. Noble metals of Group VIII(Pt and Pd) are especially suitable for hydroisomerization.Nickel-tungsten composites are especially suited for hydrocracking. Thehydrogenative metals can be composited with the zeolite by various meansknown in the art. Palladium,

for instance, is conveniently incorporated by impregnation of thezeolite with ammoniacal palladium chloride solution. When noble metalsof Group VIII are used, it is preferred that the metal content be about2%w or less. A composite containing 0.25-1 .0%w palladium on zeolitetreated according to the invention provides a highly active andefficient hydroisomerization catalyst. A composite containing about-30%w nickel and about 0.05-6%w Group VIB metal provides an active andstable hydrocracking catalyst. The catalyst is again dried and calcined.after the incorporation of hydrogenation metal. For this finalcalcination temperatures in the range of about 400-600C are suitable.Higher temperatures are not desired and can indeed result in loss ofcatalytic activity.

Catalysts prepared according to the invention are conveniently used inthe form of discrete particles,

such as granules, extrudates, pellets and the like,.

usually ranging in size from about 1/16 inch to about 1/4 inch inaverage diameter. These particles are preferably disposed in astationary bed within a suitable reactor capable of withstanding highpressure. Of course, smaller catalyst particles may be used in fluidizedor slurry reactor systems. The catalysts may also be com posited with arefractory oxide, such as by copelleting. This is particularly suitablewhere the catalysts are to be used in a fixed bed of discrete particlesin which hardness and resistance to attrition are desirable. Forexample, pellets comprising about %w alumina and about 75%w zeolitehaving an incorporated hydrogenation metal component, have been foundparticularly appropriate as isomerization catalysts. However, theconcentration of zeolite in relation to the concentration of refractoryoxide can be varied as desired. Mixtures of refractory oxides, such assilica-alumina, can also be used if desired.

The catalysts of the invention are very suitable for hydroconversionprocesses. These zinc-containing zeolites, especially those compositedwith a noble metal such as palladium of platinum, are active andsuitable for both paraffin isomerization and hydrocracking.Nickel-tungsten composites with these zeolites are also very effectivehydrocracking catalysts. These catalysts are especially effective forhydrocracking feedstocks having high organic nitrogen contents, i.e., upto about 3000 ppm.

Feed to an isomerization process using catalysts of the invention can bea substantially pure normal paraffin having from four through sevencarbon atoms, mixtures of such normalparaffins, or hydrocarbon fractionsrich in such normal paraffins. Suitable hydrocarbon fractions are the Cto C, straight-run fractions of petroleum. The catalysts can also beused in the isomerization of xylenes, e.g., the conversion of ortho andmeta-xylenes to para-xylenes.

Hydroisomerization of normal paraffins is conducted at a temperature inthe range from about 200C to 350C and preferably from about 225C to315C. At lower temperatures, conversionof normal paraffins is generallytoo low to be practical, although selectivity to isoparaffins issubstantially 100 percent. At higher temperatures, conversion of'no rmalparaffins is quite high; however, excessive cracking is encountered andselectivity to isoparaffin is extremely low asa result.

The isomerization reaction can be conducted over a wide range of spacevelocities, but in general the space velocity is in the range from about0.5 to 10 and preferably from about 1 to 5. In general, conversion ofnormal paraffins decreases with an increase in weight hourly spacevelocity (WI-ISV), although selectivity to the isoparaffin is increased.

The isomerization reaction is carried out in the presence of hydrogen;however, there is little or no net consumption of hydrogen in theprocess..Any consumption of hydrogen is the result of hydrocrackingreactions and it is preferred to keep such reactions to a minimum. Thefunction of the hydrogen is primarily to improve catalyst life,apparently by preventing polymerization of .intermediate reactionproducts which would otherwise polymerize and deposit on the catalyst. Ahydrogen to oil mole ratio of from about 1:1 to 25:1 and preferably fromabout 2:1 to 15:1 is used. It is not necessary to employ pure hydrogensince hydrogen-containing gases, e.g., hydrogen-rich gas from thecatalytic reforming of naphthas, are suitable. Total pressure is in therange from about atmospheric to 1000 pounds per square inch gauge(psig)- and preferably from about 300 to 750 psig.

The activity of zeolitic catalysts is greater than that of the amorphouscatalysts in conventional two-stage hydrocracking, but the incentive hasbeen reduced due to the increased production of C -C hydrocarbonsthrough secondary cracking reactions. By providing a basic environment,either through ammonia or organic nitrogen, compounds, this secondarycracking can be greatly reduced. Besides improving the product qualityof the hydrocracked product in conventional hydrocracking processes, thezinc-containing zeolitic catalysts of the invention can be used in otherprocess configurations. Two such configurations are singlestagehydrocracking of feedstocks containing up to 3000 ppm organic nitrogenand multistage hydrocracking of such feedstocks without removing thegaseous conversion products from prehydrogenation of the feed.

Suitable feedstocks for hydrocracking processes employing catalysts ofthe invention include any hydrocarbon boiling above the boiling range ofthe desired products. For gasoline production, hydrocarbon distillatesboiling in the range of about 200-510C are preferred. Such distillatesmay have been obtained either from distillation of crude oils, coal tar,etc., or from other processes generally applied in the oil industry suchas thermal, catalytic, or hydrogenative cracking, visbreaking,deasphalting, deasphaltenizing or combinations thereof. Since thesecatalysts are active and stable in the presence of nitrogen and sulfurcompounds, hydrofining the feedstock is optional.

Operating conditions appropriate for a hydrocracking process using thepresent catalyst include temperatures in the range of about 260C to450C, hydrogen partial pressures of about 500 to 2000 psi, liquid hourly.space velocities (LI-ISV) of about 0.2 to 10, preferably 0.5 to 5, andhydrogen/oil molar ratios of about 5 to 50.

Feed can be introduced into the reaction zone as a liquid, vapor ormixed liquid-vapor phase depending upon the temperature, pressure andamount of hydrogen mixed with the feed and the boiling range of thefeedstock utilized. The hydrogen feed, including fresh as well asrecycle feed, is usually introduced into the reaction zone with a largeexcess of hydrogen since the hydrocracking is accompanied by a ratherhigh consumption of hydrogen, usually of the order of 500-2000 standardcubic feet of hydrogen per barrel of feed. Again, any suitable hydrogencontaining gas which is predominantly hydrogen can be used. The hydrogenrich gas may optionally contain nitrogen contaminants from a feedpretreating process.

The following examples further illustrate the practice and advantages ofthe invention. Examples 1-4 relate to hydroisomerization, while Examples5-8 relate to hydrocracking.

EXAMPLE 1 A powdered sodium form of Y-faujasite zeolite ob-- tained fromthe Linde Company and designated SK-40 was used as starting material inall experiments.

A quantity of SK40 was twice contacted with 2 M l-ll-l,,N at 100C for0.5 hour each.

Three aliquots of the exchanged zeolite were incorporated with aluminum,magnesium and zinc, respectively. Aluminum ions were incorporated from asolution of 1 M A1 (S00 magnesium and zinc from their respectivenitrates. The aluminum sulfate solution had a pH of about 2.0 to obtainsufficient solubility. The other solutions had a pH of about 4.0. Afterintroduction of the metal cations, the samples were washed with water toremove unexchanged cations and split into two aliquots, one of which wascalcined at 550C and the other at 815C. Each aliquot was then twiceexchanged with 1 M NH N0 and washed with water to remove the residualsodium and again split into two aliquots, one of which was calcined at550C and the other at 815C. The cationic compositions and relativecrystallinities were determined after the first and the secondcalcination.

The catalytic activities were determined after the second calcination byconversion of n-pentane to isopentane. Since some decline in catalyticactivity occurred with all samples due to coking, the conversion wasmeasured for all catalysts after three hours of processing n-pentane.

The results obtained for the Al/Y, Mg/Y and Zn/Y- faujasite systems aresummarized in Table 1.

tion were higher for the 550C treatment than the 815C treatment.However, in all cases, the subsequent losses in relative crystallinityduring the final calcination were less for those samples that had beentreated at 815C during the intermediate calcination than for thosetreated at 550C. This effect is most apparent in the Al/Y system. Therelative crystallinities after intermediate calcination at 550C and 815Cwere completely amorphous after the final calcination while the twoaliquots treated at 815C retained relative crystallinities of 13 and 10.These observations suggest that the 815C treatment causes a greaterintrinsic loss in crystallinity than 550C treatments, but at the sametime, produces a change in the zeolite structure which increases itsstability towards further treatment. It is apparent that the combinationof an 815C intermediate calcination and a 550C final calcinationproduced the most active catalyst in all systems.

The results obtained in the Al/Y-faujasite system show significant lossin activity due to structural damage caused by the A1,(SO treatment.

The Mg/Y-faujasite appears to behave differently than any of the othersystems. The ease of removal of sodium after the intermediatecalcination is far less for this system than the others, as evidenced bythe higher sodium content of the final samples in this series. Thisresult indicates that the presence of Mg ions block the stabilizingtransformation which occurs during the high temperature calcination.

Because the actual activity of the supports were somewhat obscured bydeactivation due to coking during the catalyst testing, three of themost promising supports were ion-exchanged with ammoniacal palladiumchloride and recalcined. After reduction of the palladium, these sampleswere again tested for isomerization of n-pentane to iso-pentane. Theresults were as follows.

TABLE 2 Intermediate Calcination Percent Catalyst No. Zeolite BaseTemperature iC,, 3-B (1) Zn/Y-Faujasite 815C 43.5 2-A (l Mg/Y-Faujasite550C 10.1 2-13 (l) Mg/Y-Faujasite 815C l6.S

a) Feed n-pentane, WHSV 3.5, temperature 275C, and HJfeed 5.5.

The results demonstrate a significant activity ad- TABLE 1 Catalyst 1stcalcination: 5

2nd calcination:

Percent Na. Percent metal Relative erystallinity b Activity Calcined for3 hours.

b Crystallinity as determined by X-ray diffraction relative to untreatedSki-40. 6 Percent conversion of n-pentane after 3 hours at 300 C, 300p.s.i.g., 3.5 \\'IIS\ and IIz/pentano ratio of 4.0.

4 Aluminum. Magnesium. f Zinc.

Several general observations are noteworthy. The

relative crystallinities determined after the first calcinavantage forthe Zn-Y-faujasite base. The two Mg/Y- faujasite samples show nearly thesame activity regardless of the intermediate calcination temperature.The Zn/Y-faujasite systems show appreciable increase inactivity after an815C calcination which again suggests that the structural transformationwhich occurs during the 815 C calcination is blocked by the presence ofMg ions.

These results clearly show the advantage of zinc incorporation combinedwith a high temperature calcination and demonstrate that the finalcompositional entities are distinct species which depend upon the ionsincluded and calcination temperature.

EXAMPLE 2 Two zinc zeolites were prepared by first exchanging SK-40sodium zeolite powder with Nl-l NO at 100C, followed by contacting witha 2 M aqueous solution of zinc acetate and washing with 1 M NILNOsolution.

Samples of this material were calcined at 550C and at 800C andincorporated with platinum, then recalcined at 550C as described inExample 1. Approximately 0.5%w Pt was incorporated into all samples in astandard manner (4.3 X i M [Pt(NH C1 ]in 1M N1-l NO to eliminatedeactivation due to coking during the 4-hour tests. 7

The acidic activity of these faujasites was monitored by the extent ofisomerization of n-C to ilC s in a blend of 65%v n-C 30%v n-C and 5%vmethylcycolpentane at 250C, 450 psig, 1.0 Wl-lSV, and 2.5 H /feed ratio.The 550C calcined finished catalyst contained 0.14% Na, 1.6% Zn and hadan activity (expressed as percent hexane equilibrium obtained) of 38.8.The 800C calcined catalyst contained 0.14% Na, 2.1% Zn and had anactivity of 67.6, thus demonstrating the importance of the 800Ccalcination. It is also noteworthy that this effect is unique to thezinc catalyst.

Similarly prepared catalyst containingmagnesium or beryllium showedessentially no difference between 800C and 550C calcination. Thus, boththe incorporation of zinc and the use of calcination of about 800C isrequired to produce the composition of the present invention.

EXAMPLE 3 Another set of zinc-containing zeolites was prepared in thesame manner as for Example 2 except that the number of Nl-l NO exchangeswas varied to obtain different sodium contentsprior to the 800Ccalcination. These catalysts were then tested as in Example 2. Catalyst4A contained 0.6% Na prior to calcination, 5 .5-6.0% zinc, and about0.5% platinum, and had an activity of 52.8. For catalyst 4B whichcontained 0.26%

sodium prior to calcination, the activity was 63.0.

EXAMPLE 4 EXAMPLE 5 This example demonstrates the improved activity andstability of high-zinc content stabilized catalysts of the invention(69%w Zn) over the low-zinc catalysts 6%w Zn) in single-stagehydrocracking. A powdered form of SK-40 Y-faujasite zeolite was employedin preparation of. the base. This base was exchanged 8 times with 2 M NHNO at C for H2 hour each, refluxed with 1 M zinc acetate for 15 minutes,filtered, and washed with 0.5 M NH, N0 solution. The base was then driedfor 5 hours at 120C, cooled, and calcined for 3 hours at 800C.Approximately 20%w A1 0 was added as a hydrogel (pl-1 9.0) to thezeolite powder as a binding agent to increase the crush strength of thefinal catalyst. After aging the resultant gel for 2 hours and washing,the material was dried at 120C.

Palladium was incorporated into the base of Catalyst 6A in the standardmanner of Example 2 except that the pH of the equilibration solution wasmaintained at 4.5. The catalyst was then dried for 3 hours at 120C,calcined (in static air) for 3 hours at 200C, 3 hours at 350C and 15hours at 550C. The finished catalyst contained 0.98% Zn and 0.7 %w Pd.

Additional zinc was added to Catalyst 68 by slurrying the stabilizedzinc-Y-faujasite base for 2 hours with Zn (N0 at a pH of 5.0 after the800C calcination step. Palladium was then incorporated in the samemanner as for Catalyst 6A except that the equilibration pH was 6.0. Thefinished catalyst contained 7.2%w Zn and 0.68%w Pd.

These catalysts were then used in a single stage process to hydrocrack acatalytically cracked feedstock having a 255 APl gravity, a boilingrange of about to 360C and containing about 350 ppm organic nitrogen.Operating conditions were as follows: pressure, 1500 psig; hydrogen tooil molar ratio, 10/1; LHSV, 1.25. The temperature required to achieve aconversion of 67%w feed to products boiling below 199C was used as ameasure of catalyst performance. The test results were as follows:

TABLE 3 Temperature Required for 67%v Conversion to Products BoilingBelow 199C, C

The low zinc content catalyst 6A showed lower activity than the highzinc catalyst 6B as indicated by higher temperatures required forconversion. Catalyst 6A also showed a significantly greater activitydecline rate (temperature increase) than catalyst 68 during the firstweek of operation. Catalyst 6B rapidly reached stable operation at about370C. After 9 days operation under these conditions the requiredconversion temperature was still stable at 375C while the catalyst 6Aconversion temperature requirement continued to rise.

EXAMPLE 6 This example demonstrates the stability of a low zinc catalystof the invention 6%w) as a second stage catalyst in a hydrocrackingprocess where the organic nitrogen content of the feed to the secondstage is above 25 ppm and the effluent from a first stage is passed tothe second stage without removing ammonia or gaseous sulfur compounds.

For this test catalyst 7A was prepared in the same manner as catalyst 6A(Example 5) except that the pH of the Zn (N solution in which the basewas initially slurried was 5.5 instead of 4.5 and the final calcinationwas in flowing air rather than static air. This change was made toreduce the moisture present in the early stages of calcination. Thefinished catalyst contained 1.60%w Zn and 0.99%w Pd.

The catalyst was used in the second stage of a process to hydrocrack theeffluent from a first stage which had reduced the organic nitrogencontent of a 50/50 mixture of catalytically cracked and straight run gasoils to 30 ppm. The feed to the first stage had a 220 API gravity, aboiling range of about 2503 75C, and contained 0.6%w S and about 1300ppm nitrogen. Operating conditions were as follows: pressure, 1500 psig;hydrogen to oil molar ratio, 15/1; LHSV, 1.5. The temperature wasadjusted as required to maintain 67% conversion to products boilingbelow 199C. The test results were as follows:

TABLE 4 Temperature Required for 67%v Conversion The excellent stabilityis illustrated by the low rate of temperature increase over the testperiod.

EXAMPLE 7 This example demonstrates that a high zinc content zeolitebase (69%w Zn) is preferred over low-zinc zeolites 6%w Zn) in the secondstage of a hydrocracking process where the total effluent from the firststage is passed to the second stage without removing gaseous nitrogenand sulfur compounds and the organic nitrogen content ofthe feed to thesecond stage is above 50 ppm. The nitrogen content can rise above thislevel when the first stage catalyst has lost some of its effectivenessfor nitrogen removal.

Catalyst 68 (Example having 7.2%w zinc and catalyst 7A (Example 6)having 1.6%w zinc were tested at feed nitrogen contents of 30 and 100ppm using the same feed and operating conditions as in Example 6. Forthe 100 ppm nitrogen content the temperature of the first stage wasreduced to allow the organic nitrogen content of the first stage productto increase from 30 to 100 ppm. After stable operation was reached ateach condition the products were tested for quality. The test resultswere as follows:

TABLE 5 Catalyst 68-1 68-2 7A Organic Nitrogen to Second stage, ppm 3030 100 Hours in Operation 340 533 214 273 Second Stage Temp.,C 391 399381 395 Selectivity, %v C C, 4.0 4.3 1.9 3.2 C, 9.4 9.2 5.5 9.3 C ',-C19.3 20.2 16.2 21.7 C-,-199C 67.3 66.3 76.4 65.8 lso/Normal ParaffinRatio C, 1.7 1.5 1.6 1.4 C, 7.6 8.6 3.3 4.4 C, 16.9 19.5 6.6 8.4Hydrocarbon Type (C -199C), %v Paraffins 21.2 20.6 23.1 23.4 Naphthenes53.3 49.2 60.7 55.5 Aromatics 25.5 30.5 16.2 21.0

Where the feed has a high organic nitrogen content catalyst 613-2 issuperior to catalyst 7B in all respects, e.g., a higher selectivity to C-199C gasoline, higher iso/normal paraffin ratios and a greaterpercentage of aromatics in the gasoline fraction.

Surprisingly, catalyst 6B-2 demonstrates a promotional effect of zincwhen processing higher organic nitrogen feedstocks. Catalyst 78, as wellas other low zinc/palladium Y-faujasite catalysts, required nearly 15Chigher temperature than catalyst 7A in the second stage when thenitrogen content of the feed was increased from 30 ppm to 100 ppm.However, catalyst 6B-2 required only 8C higher temperature than catalyst6B-l for the same change in nitrogen content. Thus, it appears that theimproved performance in the presence of high organic nitrogen contentsmust be attributed to the zinc content rather than the hydrogenationactivity due to the palladium.

EXAMPLE 8 To demonstrate the versatility of zinc-containing zeolites invarious hydrocracking processes a zinc Y- faujasite was prepared by themethod used in Example 5, including the incorporation of 20%w A1 0 as abinding agent and drying at C. Nickel and tungsten were incorporatedinto the zeolites by four ion exchanges with a boiling solution of 1.0 Mnickel and 0.004 M ammonium metatungstate. The composition was washedwith boiling water after each exchange, dried at 120C for 16 hours andcalcined at 550C for 2 hours. The finished composite (catalyst 8)contained 22%w Ni; 1.9%w W; 1.3%w Zn; and 0.14%w Na.

This catalyst was used in a single-stage process to hydrocrack thecatalytically cracked feedstock of Example 5. The same operatingconditions of Example 5 were used except that the LHSV was 1.5 insteadof 1.25. After 30 days operation the temperature required to achieve aconversion of 67%w feed to products boiling below 199C was 374C. Thetemperature decline after reaching stable operation was 0.15C per day.These results show that the nickel tungsten zinc-containing zeolites arepreferred over the palladium zinc zeolites in a single stagehydrocracking process.

Catalyst 8 was then used in the second stage of a process to hydrocrackthe feedstock described in Example 6. The same operating conditions wereused, as for Example 6, except the hydrogen to oil molar ratio was 12/1instead of 15/1. After 30 days operation under these conditions thetemperature required to achieve 67%w conversion was 389C and the declinerate was 0. l C per day. For this test the feedstock was pretreated to 3ppm organic nitrogen in the first stage process. Again excellentactivity and catalyst stability were realized.

Finally, catalyst 8 was used to hydrocrack previously hydrotreatedcatalytically cracked gas oil containing 36%v aromatics, 2400 ppm sulfurand 4.2 ppm nitrogen. The feedstock had a gravity of 3.0API and aboiling range of about l50-380C. The hydrocracking conditions were:pressure, 1500 psig; LHSV, 2.0; hydrogen/oil molar ratio, 10/1. Againthe temperature was adjusted as necessary to give about 67% conversionper pass to hydrocarbons boiling below 199C. After 30 days operation thetemperature requirement was 338C and the decline rate was 02C per day.The low temperature required demonstrates the superior activity of thiscatalyst in a conventional process. The low decline rate alsodemonstrates that these catalysts have good stability.

These examples illustrate the distinct chemical nature of zeolitesprepared according to the method of my invention, which includes thecombined effects of the zinc incorporation and 800C calcination. Theyalso illustrate the feature of the preparation which can be utilized toproduct useful catalysts having high stability and acidic activitytailored to the various process needs. Thus disclosed, the numerousmeans of effective utilization of these catalysts will be apparent tothose skilled in the art.

I claim as my invention:

1. A process for the hydroconversion of a hydrocarbon fraction whichcomprises contacting a hydrocarbon feedstock in the presence of hydrogenunder suitable hydroconversion conditions with a catalyst whichcomprises a hydrogenation component selected from the group consistingof Group VIB and Group VIII and mixtures thereof, a zinc-containingcrystalline aluminosilicate zeolite having faujasite structure andalkali metal content of less than 1%w, prepared by a method whichcomprises:

a. removing alkali metal ions from an alkali metal form of zeolitehaving a faujasite structure to a level below about 1%w;

' b. incorporating zinc ions into the zeolite of reduced alkali metalcontent, followed by c. calcining at a temperature between about 775 to2. The process of claim 1 wherein the hydroconversion is thehydroisomerization of normal paraffin hydrocarbons having from four toseven carbon atoms,

the hydroisomerization conditions include a temperature of about 200 to350C, a pressure from about 300 to 750 psig, a hydrogen to oil molarratio from about 1/1 to 25/1, and a weight hourly space velocity fromabout 0.5 to 10 and the hydrocarbon component is a Group VIII noblemetal.

3. The process of claim 1 wherein the hydroconversion is thehydrocracking of a feedstock boiling substantially above the boilingrange of the desired products, the hydrocracking conditions include atemperature of about 260 to 450C, at a hydrogen partial pressure ofabout 500 to 2000 psig, a hydrogen to oil molar ratio of about 5 to 50and an LHSV of about 0.5

4. The process of claim 2 wherein the zeolite is

1. A process for the hydroconversion of a hydrocarbon fraction whichcomprises contacting a hydrocarbon feedstock in the presence of hydrogenunder suitable hydroconversion conditions with a catalyst whichcomprises a hydrogenation component selected from the group consistingof Group VIB and Group VIII and mixtures thereof, a zinc-containingcrystalline alumino-silicate zeolite having faujasite structure andalkali metal content of less than 1%w, prepared by a method whichcomprises: a. removing alkali metal ions from an alkali metal form ofzeolite having a faujasite structure to a level below about 1%w; b.incorporating zinc ions into the zeolite of reduced alkali metalcontent, followed by c. calcining at a temperature between about 775* to825*C.
 2. The process of claim 1 wherein the hydroconversion is thehydroisomerization of normal paraffin hydrocarbons havIng from four toseven carbon atoms, the hydroisomerization conditions include atemperature of about 200* to 350*C, a pressure from about 300 to 750psig, a hydrogen to oil molar ratio from about 1/1 to 25/1, and a weighthourly space velocity from about 0.5 to 10 and the hydrocarbon componentis a Group VIII noble metal.
 3. The process of claim 1 wherein thehydroconversion is the hydrocracking of a feedstock boilingsubstantially above the boiling range of the desired products, thehydrocracking conditions include a temperature of about 260* to 450*C,at a hydrogen partial pressure of about 500 to 2000 psig, a hydrogen tooil molar ratio of about 5 to 50 and an LHSV of about 0.5 to
 5. 4. Theprocess of claim 2 wherein the zeolite is washed to remove unexchangedions after step (b) and incorporated with a hydrogenation componentconsisting of platinum or palladium.
 5. The process of claim 4 whereinthe wash solution is ammonium nitrate.
 6. The process of claim 3 whereinthe zeolite is washed to remove unexchanged ions after step (b) andincorporated with a hydrogenation component consisting of nickel andtungsten after step (c).